Roasting furnace



NOV. 24, 1931. J, B, READ ET AL 1,833,590

ROASTING FURNACE Filed July 29, 1925 f5/M WML M 1 VENToRs A TTORNE Y Patented Nov. 24, 1931 UNITED STATES PATENT OFFICE JOHN BURNS READ, 0F GOLDEN,

.AND MELVILLE F. GOOLBAUGH, 0F DENVER, COLORADO,

SSIGNORS TO COMPLEX ORES RECOVEBIES COMIANY, OF DENVER, COLORADO, .A

v CORPORATION OF COLORADO noasrme remmen Application med July 29,

uel value of the ore is low, when feeding a large tonnage, or wet, or coarse ma-r terial. To maintain the ignition, it is customary to use the hot air produced by cooling the central column and rabble arms of the furnace, but in certain instances this may not be suiclent. y

The object of the present invention is to take heat, in the form of gas, away from the hottest zone of the furnace and transfer such heat to the incoming charge to evaporate moisture and ignite the ore.

The difficulty of maintaining ignition is overcome in this invention by introducing the air for oxidation at a point that is lower in the furnace than that at which the ore is introduced, preferably the second or third hearth, and allowing a portion of the air, and of the gases produced, to travel upward, and the rest to travel downward. That ortion which travels upward is conducted y a series of lues, either in the walls of the furnace or externally to the furnace, as shown in the drawing, and is re-admitted to the furnace, at or below the point at which the air is admitted, or it may even be turned directly into the llues. A series of dampers in conjunction with a fan, or without a fan, where flue draft is sufficient, are em loyed to regulate the relative pro ortions o air and gases which travel upwar and downward.

In that section of they furnace where the gases are travelling u ward, only that portion of the sulfide sul ur will be eliminated which will be neoessa to keep the charge ignited; the main desliliidizing reaction will ifgnition in the top of the furnace,

1825. Serial N0. 46,734.

take place in that section ofthe furnace where the gases and solids are traveling concurrently.

By this process heat is taken from that section of the furnace which tends to become too hot, and is distributed to that section which is not hot enough. The heat throughout the furnace is balanced in a way to prod uce more rapid and more complete oxidation of the sulfur. Ores and concentrates, whlch otherwise would not furnish a self-sustaining roast, can by this process, be roasted efficiently without the use of extraneous fuel.

In the drawing, the process is disclosed as being carried out in a superposed hearth furnace, although other conventional types of furiace can, with suitable modifications, be use Referring to the drawing for a more complete disclosure of the invention The ligure is a vertical section of one t e of furnace suitably modified to carry out t e process.

. The furnaceis provided with a plurality of superposed hearths 2 and a hollow vertical rotary shaft 3, having secured thereto rabble arms 4. Alternate hearthsare provided respectively with central openings 5 and peripheral openings 6, through which the ore drops as it travels from hearthl to hearth.

The upper end of the hollow vertical shaft 3 is connected to a flue 7, which is provided with branches 8, 9, and lO leading into the space above the second, third and fourth hearths and below the top hearth. The space above the top hearth is connected to a flue 11, which may be connected to a suction fan 12, the said flue 4l1 being provided; with .branch lues 13, 14, 15 and 16, leading into which are below the various fiues for controlling the direction and amount of flow of the various gases,

Operation Il Ore is fed into the up er part of the furnace through the feed opper 17 onto the upper hearth. The roasting process will start by drying and igniting the sulfide ore on the first hearth. The ore will continue to roast l on the hearths below the first hearth, and will be discharged, usually at a high temperature, through'the calcine discharge 18. Gold air fed into the bottom of the hollow column 3 will be substantially raised in temperature as l5 it enters the I'iue 7 on its way to the branch flues 8, 9, and 10. The air entering thrugh the flue 8 below thetop hearth will 1n a large part pass upward together with hot gases into contact with the ore on the top hearth, roviding therebl the necessary heat for drymg the ore and e ecting ignition. The heated air passing through the branch fines 9 and 10 will furnish the necessary oxygen for combustion on the third and fourth hearths and lower hearths, the gases over these hearths travelling concurrently with the ore and being carried off through the flue 10a. It may be advisable to use one, two, or three lues for the introduction of air to the furnace or any combination of liues 8, 9 and 10. In

any combination for introducing air a portion of it will travel upward and the remainder downward.

The direction, of flow of gases on the hearths will be controlled in part by the fan 12. The fan is rotated so that the gases above the top hearth will be drawn into the iue 11, thus producing an upward current above the top hearths, whereas the fan will force the gases through the branch flues 18, 14, 15 and 16, or any o these, thus causinga downward movement of gases over the ore on these hearths. The ore is stirred and moved from hearth to hearth in the customaryfmanner by the rotating rabble arms 4.

What we claim, is:

1. A roasting furnace provided with superposed hearths, an ore feed at the top of the furnace, and means for feeding air into the 60 furnace below the top hearth and above the bottom hearths, a po'rtion of the air traveling upwards and the remainder downwards. 2. A roasting furnace provided with superosed hearths, an ore feed atthe top of the urnace, means for feeding hot gases upwardly onto the upper hearth and downwardly onto the lower hearths.

8. lA roasting furance provided with superos'ed hearths, an ore feed at the top of the i urnace, means for feeding air into the'furnace below the top hearth and above the bottom hearths, a portion of the air traveling upwards and the remainder downwards, and

means for exhausting gases from above the top hearth.

`posed hearths, an ore feed at the top of the 4. A roasting furnace provided with superosed hearths, an ore feed at the top of the urnace, means for feeding air into the furnace below the top hearth and above the bottom hearths a portion of the air traveling upwards and the remainder downwards, and means for exhausting gases from above the top hearth and feeding the said gases onto the bottom hearths.

5. A roasting furnace provided with superposed hearths, an ore feed at the top of the furnace, means for feeding hot gases upwardly onto the upper hearth and downwardly onto the lower hearths, means for exhausting the upwardly moving gases from above the top hearth and for exhausting the downward ly moving gases at the bottom of the furnace 6. A roasting furnace provided with su erposed hearths, an ore feed at the top o the furnace and a calcine discharge at the botv tom of the furnace, means Ifor continuously moving the ore through the furnace, means for feeding hot gases over the top hearth in a direction opposite to the direction in which the ore is moving, and means for feeding air for oxidation and hot gases over the lower hearths in the same direction as the ore is moving.

7. A roasting furnace provided with superfurnace, means for feedin hot vases upwardly onto the upper hearth an downwardly onto the lower hearths, means for exhausting the upwardly moving gases from above the top hearth and for exhausting the downwardly moving gases at the bottom of the furnace, and means for feeding exhaust gases back onto the lower hearths.

8. A roasting furnace for sulphide ores provided with means for feeding ore at one end and discharging it at the other end, means for feeding air for oxidation intermediate the said ends, and means for moving hot 4 gases over the ore at the feed end of the furnace to ignite the said ore. 11

9. A roasting furnace for sulphide ores provided with means for feeding ore at one end and discharging it at the other end, means for feeding air for oxidation intermediate the said ends, means for moving hot gases over the ore at the feed end of the furnace to ignite the said ore, and means for moving air, gases and ore in the same direction between the means for feeding air and the discharge end to desulphidize the said ore. 15

10. A roasting furnace comprising the combination with a plurality of communicating superposed hearths, of a hollow/shaft passing through the hearths, means for admitting air into the shaft adjacent the bottom thereof, a 1f conduit communicating with the shaft near the top thereof, the said conduit being provided with branches leading below the top hearth and above the bottom hearths, whereby air heated inthe hotter regions of the fur- 1i nace may be supplied to the cooler portions of the furnace to facilitate the drung and roasting of material placed upon t e cooler hearths, conduit `for withdrawin the products of combustion from the saidxearths.

1l. A roasting furnace comprising a. lurality of superposed hearths, a hollow s aft passing through the said hearths, means for admitting air into the shaft adjacent the bottom thereof, a branched conduit connecting the upper portion of the said shaft with a selected plurality of hearths, whereby the air passing through the shaft becomes heated in the hotter portions of the furnace and is discharged into the cooler portions thereof, the heat of the said air being utilized to facilitate combustion in the cooler portions of the furnace, and means for exhausting the prodr ucts of combustion from the to and bottom portions of the furnace, where of the admitted air and of the furnace gases travels upwards and the remainder downwards.

. urnace,

12. In a roasting furnace'comprisin imposed hearths having passa for moving the ore downwar to hearth, means for producing superesvan means from hearth a current of air counter to the direction of the ore movement through Vthe upper portion of the fur-y nace, for creating a zone of maximum air ressure in an intermediate portion of the i) and for roducing a current of air in the direction ofpore movement in the lower portion of the furnace. 13. In a roasting furnace comprisin superimposed hearths having passages an means for movingore from hearth to hearth from the top hearth down through the lower hearth, an air outlet at the top hearth,A an air outlet at the lower hearth, and an air inlet at an intermediate hearth having connection through the respective hearths with said top and bottom outlets. A

14. In a roasting furnace comprising superimposed hearths having passages an means for moving ore from hearth to hearth from `the top hearth down through the lower hearth, an air outlet at the top hearth, an air outlet at the bottom hearth, and an air inlet opening into two consecutive intermediate hearths.

15. .In a roasting furnace comprisin imposed hearths having passages an for moving ore from the top hearth down through the lower hearth, an air outlet at the top hearth, an air outlet at the bottom hearth, and an air inlet opening into two consecutive intermediate hearths, and means for causing such air movesupermeans ments in opposite directions in the furnace.

In testimony whereof, we -aix our signatures.

JOI-IN BURNS READ. MELVILLE F. COOLBAUGH.

and means independent of the said y a portion hearth to hearth from 

